Kinesiology and Health Sciences

Permanent URI for this collectionhttps://uwspace.uwaterloo.ca/handle/10012/9862

This is the collection for the University of Waterloo's Department of Kinesiology and Health Sciences. It was known as the Department of Kinesiology until January 2021.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

Waterloo faculty, students, and staff can contact us or visit the UWSpace guide to learn more about depositing their research.

Browse

Browsing Kinesiology and Health Sciences by Subject "ACL"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    ACL Injury Mechanisms and the Kinetic Chain Linkage: The effect of proximal joint stiffness on ACL injury risk.
    (University of Waterloo, 2016-08-30) Cannon, Jordan
    Recent literature has suggested that core and gluteal neuromuscular deficits are involved in the mechanism of non-contact ACL injury. Several research groups have identified dynamic valgus of the lower extremity to be an injurious posture that is predictive of future non-contact ACL injury risk. Aberrant kinematics of segments proximally in the kinetic chain, namely the trunk and hip, have also been observed to drive dynamic valgus during dynamic activities. Comprehensive investigation of the neuromuscular deficits postulated as the mechanism of injurious mechanics are lacking in the literature. Given that certain motions can be created by infinite muscle activation combinations, and that muscle activation contributes both force and controlling stiffness, this work aims to characterise any such deficits by examining the ability to modulate proximal joint stiffness to dynamically control distal segments of the kinetic chain. Three-dimensional lumbar spine stiffness and hip stiffness were quantified in participants deemed as ‘high valgus’ and ‘low valgus’ based on their frontal plane knee displacement during each task. The risk of non-contact ACL damage is highest among active females, justifying their choice to study. Eighteen female participants completed drop vertical jump (DVJ), stop jump (SJ), single leg drop (SLD) and single leg crossover drop (SLCD) tasks in order to measure medial knee displacement and associated proximal joint stiffness values. It was hypothesized that those with high valgus would not generate sufficient joint rotational stiffness at the lumbar spine, hip, or both, and thus aberrant kinematics and the injurious dynamic valgus motion would result. Those who were able to develop sufficient stiffness at the lumbar spine and hip had greater control over the kinetic chain and in doing so reduced dynamic valgus and likely their risk of future ACL injury. However, variance within subjects was found, specifically the same person would show a valgus landing on one trial, but not on another. This necessitated a change in analysis to one considering the landings as case studies, and groupings of landings by whether valgus occurred or not, rather than by subjects. This was an unexpected, and therefore exciting part of the thesis journey. The results here provide insight into the motor control component of avoiding dynamic valgus and is the first work to confirm, and specifically characterize, a neuromuscular deficit at the core or hip. That deficit appears to be an inability to generate sufficient joint rotational stiffness in order to control the linkage. Given this insight, appropriate interventions and training programs may be designed to reduce one’s risk of ACL injury.
  • Thumbnail Image
    Item
    Passive Frontal Plane Knee Joint Laxity Following Anterior Cruciate Ligament Reconstruction Within 6 Months to 5 Years
    (University of Waterloo, 2022-01-28) Loo, Michelle
    Following an anterior cruciate ligament rupture, surgical reconstructions aim to restore the joint stability. Increased frontal plane laxity has been observed in the anterior cruciate ligament deficient knee, intra-operatively immediately following reconstruction compared to contralateral knees, and in osteoarthritic knees. This indicates that surgical intervention may not have fully mitigated the increased frontal plane laxity associated with an anterior cruciate ligament tear. The primary objective of this study was to compare passive frontal plane laxity in a relatively young study cohort (aged 19-24) across three knee statuses (anterior cruciate ligament reconstructed knees (between 6 months to 5 years post-operation), contralateral knees, and knees from a control group), taking into account sex. It was hypothesized that the anterior cruciate ligament reconstructed knees would have the greatest frontal plane laxity, followed by the contralateral knees, and finally the control knees, where females would have a greater laxity compared to males across all three knee statuses. A secondary objective of this study was to quantify the repeatability and sensitivity of the frontal plane measurement system following design modifications that: removed the effect of the gravitational force from the plane of measurement, applied a consistent load between participants, allowed rotation about the knee’s natural joint center, and monitored muscle activity that ensured passive laxity measures. It was hypothesized that the frontal plane measurement system of this study would have a greater repeatability and sensitivity compared to previous designs reported in the literature. Twenty-four university aged participants (twelve females mean age 20.5 ± 1.8 and twelve males mean age 21.7 ± 2.3) were recruited for this cohort study. There were two groups: twelve participants with one ACL reconstructed knee and one contralateral knee (that had no previous ACL tear or repair) and twelve age- and sex-matched controls. Of the ACL reconstructed participants, six received a bone-patellar tendon-bone autograft and six received a hamstring autograft during their ACL reconstruction. Passive bilateral lower limb kinematic data was collected using infrared marker clusters while vastus lateralis and vastus medialis electromyographic readings were recorded. The mean laxity from three trials was measured using a free moving sled apparatus. Frontal plane laxity was defined as the passive varus-valgus tibiofemoral angular excursion in response to a varus-valgus moment of 10 Nm. For controls, the knee with the greatest measured mean frontal plane laxity was used. The standard error of measurement and minimal detectable difference was calculated using the mean of the three repeated laxity measures for the right limb across all participants. The means of the three repeated laxity measures for each knee status (ACL reconstructed knees, contralateral knees, and controls knees) were used in one two-way mixed model analysis of variance between ACL reconstructed knees and contralateral knees (status x sex) with an alpha level of 0.05 and two additional two-way ANOVA between ACL reconstructed knees and controls knees, and contralateral knees and control knees (status x sex) with an alpha level of 0.05. One t-test with an alpha level of 0.05 was used to determine if there were any statistically significant differences between the type of surgical reconstruction (bone-patellar tendon-bone graft or hamstring graft). The standard error of measurement and mean detectable difference was 0.7° and 1.8° respectively. No statistically significant knee status main effect, sex main effect and knee status x sex interaction occurred (all p>0.05). There was no significant difference in laxity between reconstruction types (p>0.05). This sample population achieved normal frontal plane knee laxity at short-term follow-up. This supports the possibility that the laxity previously measured in long-term follow-up is not residual laxity from the anterior cruciate ligament rupture that was insufficiently addressed by the reconstruction procedure. Increased frontal plane laxity that has been observed in anterior cruciate ligament reconstructed and osteoarthritic knees may instead be an outcome of the disease itself or other risk factors.